[coroutines] Add codegen for await and yield expressions
Details:
Emit suspend expression which roughly looks like:
auto && x = CommonExpr();
if (!x.await_ready()) {
llvm_coro_save();
x.await_suspend(...); (*)
llvm_coro_suspend(); (**)
}
x.await_resume();
where the result of the entire expression is the result of x.await_resume()
(*) If x.await_suspend return type is bool, it allows to veto a suspend:
if (x.await_suspend(...))
llvm_coro_suspend();
(**) llvm_coro_suspend() encodes three possible continuations as a switch instruction:
%where-to = call i8 @llvm.coro.suspend(...)
switch i8 %where-to, label %coro.ret [ ; jump to epilogue to suspend
i8 0, label %yield.ready ; go here when resumed
i8 1, label %yield.cleanup ; go here when destroyed
]
llvm-svn: 298784
diff --git a/clang/lib/CodeGen/CGCoroutine.cpp b/clang/lib/CodeGen/CGCoroutine.cpp
index 77497f3..7dd8e05 100644
--- a/clang/lib/CodeGen/CGCoroutine.cpp
+++ b/clang/lib/CodeGen/CGCoroutine.cpp
@@ -12,35 +12,58 @@
//===----------------------------------------------------------------------===//
#include "CodeGenFunction.h"
+#include "llvm/ADT/ScopeExit.h"
#include "clang/AST/StmtCXX.h"
using namespace clang;
using namespace CodeGen;
-namespace clang {
-namespace CodeGen {
+using llvm::Value;
+using llvm::BasicBlock;
-struct CGCoroData {
+namespace {
+enum class AwaitKind { Init, Normal, Yield, Final };
+static constexpr llvm::StringLiteral AwaitKindStr[] = {"init", "await", "yield",
+ "final"};
+}
- // Stores the jump destination just before the final suspend. Coreturn
+struct clang::CodeGen::CGCoroData {
+ // What is the current await expression kind and how many
+ // await/yield expressions were encountered so far.
+ // These are used to generate pretty labels for await expressions in LLVM IR.
+ AwaitKind CurrentAwaitKind = AwaitKind::Init;
+ unsigned AwaitNum = 0;
+ unsigned YieldNum = 0;
+
+ // How many co_return statements are in the coroutine. Used to decide whether
+ // we need to add co_return; equivalent at the end of the user authored body.
+ unsigned CoreturnCount = 0;
+
+ // A branch to this block is emitted when coroutine needs to suspend.
+ llvm::BasicBlock *SuspendBB = nullptr;
+
+ // Stores the jump destination just before the coroutine memory is freed.
+ // This is the destination that every suspend point jumps to for the cleanup
+ // branch.
+ CodeGenFunction::JumpDest CleanupJD;
+
+ // Stores the jump destination just before the final suspend. The co_return
// statements jumps to this point after calling return_xxx promise member.
CodeGenFunction::JumpDest FinalJD;
- unsigned CoreturnCount = 0;
-
// Stores the llvm.coro.id emitted in the function so that we can supply it
// as the first argument to coro.begin, coro.alloc and coro.free intrinsics.
// Note: llvm.coro.id returns a token that cannot be directly expressed in a
// builtin.
llvm::CallInst *CoroId = nullptr;
+
// If coro.id came from the builtin, remember the expression to give better
// diagnostic. If CoroIdExpr is nullptr, the coro.id was created by
// EmitCoroutineBody.
CallExpr const *CoroIdExpr = nullptr;
};
-}
-}
+// Defining these here allows to keep CGCoroData private to this file.
clang::CodeGen::CodeGenFunction::CGCoroInfo::CGCoroInfo() {}
CodeGenFunction::CGCoroInfo::~CGCoroInfo() {}
@@ -66,6 +89,126 @@
CurCoro.Data->CoroIdExpr = CoroIdExpr;
}
+// Synthesize a pretty name for a suspend point.
+static SmallString<32> buildSuspendPrefixStr(CGCoroData &Coro, AwaitKind Kind) {
+ unsigned No = 0;
+ switch (Kind) {
+ case AwaitKind::Init:
+ case AwaitKind::Final:
+ break;
+ case AwaitKind::Normal:
+ No = ++Coro.AwaitNum;
+ break;
+ case AwaitKind::Yield:
+ No = ++Coro.YieldNum;
+ break;
+ }
+ SmallString<32> Prefix(AwaitKindStr[static_cast<unsigned>(Kind)]);
+ if (No > 1) {
+ Twine(No).toVector(Prefix);
+ }
+ return Prefix;
+}
+
+// Emit suspend expression which roughly looks like:
+//
+// auto && x = CommonExpr();
+// if (!x.await_ready()) {
+// llvm_coro_save();
+// x.await_suspend(...); (*)
+// llvm_coro_suspend(); (**)
+// }
+// x.await_resume();
+//
+// where the result of the entire expression is the result of x.await_resume()
+//
+// (*) If x.await_suspend return type is bool, it allows to veto a suspend:
+// if (x.await_suspend(...))
+// llvm_coro_suspend();
+//
+// (**) llvm_coro_suspend() encodes three possible continuations as
+// a switch instruction:
+//
+// %where-to = call i8 @llvm.coro.suspend(...)
+// switch i8 %where-to, label %coro.ret [ ; jump to epilogue to suspend
+// i8 0, label %yield.ready ; go here when resumed
+// i8 1, label %yield.cleanup ; go here when destroyed
+// ]
+//
+// See llvm's docs/Coroutines.rst for more details.
+//
+static RValue emitSuspendExpression(CodeGenFunction &CGF, CGCoroData &Coro,
+ CoroutineSuspendExpr const &S,
+ AwaitKind Kind, AggValueSlot aggSlot,
+ bool ignoreResult) {
+ auto *E = S.getCommonExpr();
+ auto Binder =
+ CodeGenFunction::OpaqueValueMappingData::bind(CGF, S.getOpaqueValue(), E);
+ auto UnbindOnExit = llvm::make_scope_exit([&] { Binder.unbind(CGF); });
+
+ auto Prefix = buildSuspendPrefixStr(Coro, Kind);
+ BasicBlock *ReadyBlock = CGF.createBasicBlock(Prefix + Twine(".ready"));
+ BasicBlock *SuspendBlock = CGF.createBasicBlock(Prefix + Twine(".suspend"));
+ BasicBlock *CleanupBlock = CGF.createBasicBlock(Prefix + Twine(".cleanup"));
+
+ // If expression is ready, no need to suspend.
+ CGF.EmitBranchOnBoolExpr(S.getReadyExpr(), ReadyBlock, SuspendBlock, 0);
+
+ // Otherwise, emit suspend logic.
+ CGF.EmitBlock(SuspendBlock);
+
+ auto &Builder = CGF.Builder;
+ llvm::Function *CoroSave = CGF.CGM.getIntrinsic(llvm::Intrinsic::coro_save);
+ auto *NullPtr = llvm::ConstantPointerNull::get(CGF.CGM.Int8PtrTy);
+ auto *SaveCall = Builder.CreateCall(CoroSave, {NullPtr});
+
+ auto *SuspendRet = CGF.EmitScalarExpr(S.getSuspendExpr());
+ if (SuspendRet != nullptr) {
+ // Veto suspension if requested by bool returning await_suspend.
+ assert(SuspendRet->getType()->isIntegerTy(1) &&
+ "Sema should have already checked that it is void or bool");
+ BasicBlock *RealSuspendBlock =
+ CGF.createBasicBlock(Prefix + Twine(".suspend.bool"));
+ CGF.Builder.CreateCondBr(SuspendRet, RealSuspendBlock, ReadyBlock);
+ SuspendBlock = RealSuspendBlock;
+ CGF.EmitBlock(RealSuspendBlock);
+ }
+
+ // Emit the suspend point.
+ const bool IsFinalSuspend = (Kind == AwaitKind::Final);
+ llvm::Function *CoroSuspend =
+ CGF.CGM.getIntrinsic(llvm::Intrinsic::coro_suspend);
+ auto *SuspendResult = Builder.CreateCall(
+ CoroSuspend, {SaveCall, Builder.getInt1(IsFinalSuspend)});
+
+ // Create a switch capturing three possible continuations.
+ auto *Switch = Builder.CreateSwitch(SuspendResult, Coro.SuspendBB, 2);
+ Switch->addCase(Builder.getInt8(0), ReadyBlock);
+ Switch->addCase(Builder.getInt8(1), CleanupBlock);
+
+ // Emit cleanup for this suspend point.
+ CGF.EmitBlock(CleanupBlock);
+ CGF.EmitBranchThroughCleanup(Coro.CleanupJD);
+
+ // Emit await_resume expression.
+ CGF.EmitBlock(ReadyBlock);
+ return CGF.EmitAnyExpr(S.getResumeExpr(), aggSlot, ignoreResult);
+}
+
+RValue CodeGenFunction::EmitCoawaitExpr(const CoawaitExpr &E,
+ AggValueSlot aggSlot,
+ bool ignoreResult) {
+ return emitSuspendExpression(*this, *CurCoro.Data, E,
+ CurCoro.Data->CurrentAwaitKind, aggSlot,
+ ignoreResult);
+}
+RValue CodeGenFunction::EmitCoyieldExpr(const CoyieldExpr &E,
+ AggValueSlot aggSlot,
+ bool ignoreResult) {
+ return emitSuspendExpression(*this, *CurCoro.Data, E, AwaitKind::Yield,
+ aggSlot, ignoreResult);
+}
+
void CodeGenFunction::EmitCoreturnStmt(CoreturnStmt const &S) {
++CurCoro.Data->CoreturnCount;
EmitStmt(S.getPromiseCall());
@@ -78,11 +221,13 @@
unsigned NewAlign = TI.getNewAlign() / TI.getCharWidth();
auto *FinalBB = createBasicBlock("coro.final");
+ auto *RetBB = createBasicBlock("coro.ret");
auto *CoroId = Builder.CreateCall(
CGM.getIntrinsic(llvm::Intrinsic::coro_id),
{Builder.getInt32(NewAlign), NullPtr, NullPtr, NullPtr});
createCoroData(*this, CurCoro, CoroId);
+ CurCoro.Data->SuspendBB = RetBB;
EmitScalarExpr(S.getAllocate());
@@ -90,10 +235,12 @@
EmitStmt(S.getPromiseDeclStmt());
+ CurCoro.Data->CleanupJD = getJumpDestInCurrentScope(RetBB);
CurCoro.Data->FinalJD = getJumpDestInCurrentScope(FinalBB);
// FIXME: Emit initial suspend and more before the body.
+ CurCoro.Data->CurrentAwaitKind = AwaitKind::Normal;
EmitStmt(S.getBody());
// See if we need to generate final suspend.
@@ -105,6 +252,8 @@
}
EmitStmt(S.getDeallocate());
+ EmitBlock(RetBB);
+
// FIXME: Emit return for the coroutine return object.
}
diff --git a/clang/lib/CodeGen/CGExprAgg.cpp b/clang/lib/CodeGen/CGExprAgg.cpp
index 0092447..fdf8e6a 100644
--- a/clang/lib/CodeGen/CGExprAgg.cpp
+++ b/clang/lib/CodeGen/CGExprAgg.cpp
@@ -111,6 +111,13 @@
void VisitGenericSelectionExpr(GenericSelectionExpr *GE) {
Visit(GE->getResultExpr());
}
+ void VisitCoawaitExpr(CoawaitExpr *E) {
+ CGF.EmitCoawaitExpr(*E, Dest, IsResultUnused);
+ }
+ void VisitCoyieldExpr(CoyieldExpr *E) {
+ CGF.EmitCoyieldExpr(*E, Dest, IsResultUnused);
+ }
+ void VisitUnaryCoawait(UnaryOperator *E) { Visit(E->getSubExpr()); }
void VisitUnaryExtension(UnaryOperator *E) { Visit(E->getSubExpr()); }
void VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *E) {
return Visit(E->getReplacement());
diff --git a/clang/lib/CodeGen/CGExprComplex.cpp b/clang/lib/CodeGen/CGExprComplex.cpp
index 22e7fa6..9809723 100644
--- a/clang/lib/CodeGen/CGExprComplex.cpp
+++ b/clang/lib/CodeGen/CGExprComplex.cpp
@@ -110,6 +110,16 @@
VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *PE) {
return Visit(PE->getReplacement());
}
+ ComplexPairTy VisitCoawaitExpr(CoawaitExpr *S) {
+ return CGF.EmitCoawaitExpr(*S).getComplexVal();
+ }
+ ComplexPairTy VisitCoyieldExpr(CoyieldExpr *S) {
+ return CGF.EmitCoyieldExpr(*S).getComplexVal();
+ }
+ ComplexPairTy VisitUnaryCoawait(const UnaryOperator *E) {
+ return Visit(E->getSubExpr());
+ }
+
// l-values.
ComplexPairTy VisitDeclRefExpr(DeclRefExpr *E) {
diff --git a/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp
index 67f821f..4e17f36 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -276,6 +276,15 @@
Value *VisitGenericSelectionExpr(GenericSelectionExpr *GE) {
return Visit(GE->getResultExpr());
}
+ Value *VisitCoawaitExpr(CoawaitExpr *S) {
+ return CGF.EmitCoawaitExpr(*S).getScalarVal();
+ }
+ Value *VisitCoyieldExpr(CoyieldExpr *S) {
+ return CGF.EmitCoyieldExpr(*S).getScalarVal();
+ }
+ Value *VisitUnaryCoawait(const UnaryOperator *E) {
+ return Visit(E->getSubExpr());
+ }
// Leaves.
Value *VisitIntegerLiteral(const IntegerLiteral *E) {
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 7e99bdb..4a7cc02 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -1986,7 +1986,7 @@
/// pointer to a char.
Address EmitMSVAListRef(const Expr *E);
- /// EmitAnyExprToTemp - Similary to EmitAnyExpr(), however, the result will
+ /// EmitAnyExprToTemp - Similarly to EmitAnyExpr(), however, the result will
/// always be accessible even if no aggregate location is provided.
RValue EmitAnyExprToTemp(const Expr *E);
@@ -2528,6 +2528,12 @@
void EmitCoroutineBody(const CoroutineBodyStmt &S);
void EmitCoreturnStmt(const CoreturnStmt &S);
+ RValue EmitCoawaitExpr(const CoawaitExpr &E,
+ AggValueSlot aggSlot = AggValueSlot::ignored(),
+ bool ignoreResult = false);
+ RValue EmitCoyieldExpr(const CoyieldExpr &E,
+ AggValueSlot aggSlot = AggValueSlot::ignored(),
+ bool ignoreResult = false);
RValue EmitCoroutineIntrinsic(const CallExpr *E, unsigned int IID);
void EnterCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock = false);